Iron and steel are used widely in the construction of roads, railways, other infrastructure, appliances, and buildings. Most large modern structures, such asstadiumsandskyscrapers,bridges, andairports, are supported by a steel skeleton. Even those with a concrete structure employ steel for reinforcing. In addition, it sees widespread use inmajor appliancesandcars. Despite growth in usage ofaluminium, it is still the main material for car bodies. Steel is used in a variety of otherconstructionmaterials, such as bolts,nails, andscrews.

Other common applications includeshipbuilding,pipeline transport,mining,offshore construction,aerospace,white goods(e.g.washing machines),heavy equipmentsuch as bulldozers, office furniture,steel wool,tools, andarmourin the form of personal vests orvehicle armour(better known asrolled homogeneous armourin this role). Steel was the metal of choice for sculptorJim Garyand a frequent choice forsculptureby many other modern sculptors.

Firstly, The structuralsteel，1>The construction and engineering with the structural steel is called construction steel, it is used in building, bridges, ships, boilers or other engineering, it is the production of the metal structure of the steel. Such as carbon steel, low alloy steel, reinforced steel.2>Machinery manufacturing structural steel- steel structural parts for manufacturing machinery and equipment. For his style of steel, it is basically a high-quality steel or high-quality steel, mainly has quality carbon structural steel, alloy structural steel, easy to cut structural steel, spring steel, bearing steel, etc.

Generally used in the manufacture of a variety of tools, such as carbon tool steel, alloy tool steel, high speed tool steel, etc. According to the usage, it can be divided into cutting tool steel, die steel, gauge steel.

This means the steel professional use of the various industrial sectors, such as automotive steel, farm machinery steel, aviation and steel, chemical machinery steel, boiler steel, electrical steel, welding rod steel.

(3) High quality steel, fewer elements containing impurities in the steel ,S≤ O.03%,P ≤ 0.035%, such as alloy structural steel and tool steel. High quality steel behind the steel grade, it is usually added the symbol "A" or the Chinese character "high" in order to be recognized.